Not much to say about this area. No monsters, no NPCs, no treasure, just four doors. One leads back outside to the Dungeon Exit, one to The Mines, one to the Hall Of Doors and the last to the Soldier's Quarters. It's 9 by 11 in size.
In the top left corner is a locked door which you can't enter until your character is Level 20 or above and has the Thieves' Key. This then gives a short cut to Level 6 - Labyrinth I. All quest items relating to the palace are taken from you when you enter, which is worrying, to say the least, when it happens!
NOTE: All quest items related to the palace are taken from you the first time you enter this door, but nothing is taken from you (e.g. - quest items relating to the palace) on subsequent entries.